What is the force that causes deformation parallel to a plane, analogous to torsion on a horizontal plane?

• A. Bending
• B. Tension
• C. Compression
• D. Shear

Answer: (D)

Shear is the deformation that occurs when adjacent layers slide past each other in a direction parallel to the plane of contact. A shear force tries to slide one layer relative to the layer next to it, producing a distortion that makes the element resemble a parallelogram. In a beam, the internal shear stress acts parallel to the cross‐section, causing this parallel-to-plane distortion, which is the same type of deformation you'd get from torsion on a plane twisting the material. Tension and compression, by contrast, stretch or shorten along the axis and act perpendicular to the plane, and bending combines these normal strains rather than producing pure sliding parallel to a plane.